Anterior plating system and method

ABSTRACT

Systems and methods for stabilizing the spine are provided. For stabilizing the L 5 -S 1  junction, the system includes a plate that has a generally triangular shape with an upper node and a pair of lower nodes. The upper node has a hole through the plate to receive a screw for passage into the L 5  vertebra. The lower nodes each include a hole through the plate to receive screws for passage into the S1 vertebra. The system further includes a plate having a retaining element for preventing backout of screws inserted through the plate. Instruments and methods for attaching the plate to the spinal column are also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.09/993,860, filed on Nov. 6, 2001, which claims foreign prioritybenefits under Title 35, United States Code, §119 to French PatentApplication No. 01 04728, filed Apr. 6, 2001.

FIELD OF THE INVENTION

The present invention relates generally to instruments and methods forspinal stabilization, and more particularly to spinal plating systemsand methods.

BACKGROUND

Various types of plating devices and systems have been used to stabilizeportions of the spine. For cases in which interbody fusion is desired inthe lumbro-sacral region, stabilization using posterior plating has beenpreferred by many surgeons for good fixation and to avoid damage to thevascular and nervous system components adjacent the anterior surfaces ofthe L5 vertebra. A posterior plating system for stabilization of theL5-S1 junction is disclosed in U.S. Pat. No. 5,127,912 issued Jul. 7,1992 to Ray and Ashman.

While posterior fixation systems are often used in fusions, the anteriorsurgical approach for insertion of fusion devices is preferred fromseveral perspectives. Less blood loss and reduced post-operative paincan be achieved, and there is risk of traumatizing nerves. Additionally,the posterior approach impairs muscles, which are vascularized, andligaments, which are cut. Effective anterior plating could generallyavoid the risks associated with posterior surgery, particularly if ananterior approach is used which is also as minimally invasive aspossible, since it is then only necessary to move aside soft tissueswhich do not affect the stability of the spinal column.

There is however one zone of the spine where an anterior approachentails a particular risk: the zone corresponding to lumbar vertebraeL4-L5 and the first sacral vertebra S1. In this region, the aorta andthe vena cava divide to form the right and left iliac veins andarteries. There is therefore a risk of damaging an important bloodvessel during implantation of a conventional fixation system. There isalso a risk that important blood vessels could be damaged by screwbackout, or simply by protrusion of the plate against the blood vessel.Moreover, between the profiles of vertebrae L5 and S1 there is an anglecalled the “promontory angle” which is very variable from one individualto another. There can also be sliding between L5 and S1(spondylolisthesis). These conditions further increase the difficultyand risk factors associated with attachment of a stabilization deviceanteriorly to the L5-S1 region.

There remains a need for anterior plating systems and methods to providestability for fusion between vertebrae that is adapted to address thechallenges presented above.

SUMMARY

Described briefly according to the illustrated embodiments of theinvention, a stabilizer for the lumbar/sacral junction is provided. Thestabilizer includes a plate having a generally triangular shape with anupper node and a pair of lower nodes. The upper node has an upper holeto receive a screw for passage into an upper vertebra, such as L5. Thelower nodes each include a hole to receive a screw for passage into alower vertebra, such as S1.

There is also provided a plate for a device for stabilization ofvertebrae L5 and S1 that has a generally triangular shape, and includesnear its upper vertex, a hole through which a screw is passed for fixingthe plate to L5, and two holes situated near its lower vertices throughwhich screws are passed for fixing the plate to S1.

The present invention also provides an anterior spinal plate system thathas a plate with a generally triangular shape and includes on itsposterior face a protrusion which extends along at least part of thewidth of the plate that bears against the lower anterior lip of thelower endplate of L5.

The present invention additionally provides an anterior spinal platesystem that has a plate with a triangular shape and includes, on itsposterior face near its lower vertices, protrusions which are intendedto come to bear against the lower margin of the salient part of S1. Theplate can further include on the edge of its posterior face, in theregion of its upper vertex, a ridge-shaped protrusion or at least oneanchoring point or spike to contact or anchor in L5.

The present invention further provides an anterior spinal plate systemthat has a plate with an upper face, a lower face, and at least one holetherethrough extending between the upper and lower faces. A retainingelement extends from the upper face of the plate adjacent the at leastone hole. The retaining element has a first form wherein a screw isinsertable into the at least one hole and is formable to a second formwherein at least a portion of the retaining element extends over the atleast one hole, blocking the screw in the hole.

The present invention further provides an anterior spinal plate systemthat includes a plate having a triangular shape and an upper face, alower face, and holes therethrough extending between the upper and lowerfaces at each vertex. A retaining element is provided to prevent screwbackout. In one form, the retaining element can be clipped, screwed orotherwise secured to the anterior face of the plate and is capable of atleast partially covering the holes passed through by the screws. Theretaining element can be of substantially circular shape, substantiallytriangular shape, or spoke shaped.

The invention also provides a system for osteosynthesis of the spine forjoining vertebrae L5 and S1. The system includes a triangular platehaving an upper vertex oriented over L5 and two lower vertices orientedover S1. Each vertex has a hole through which a screw may be passed. Thesystem further includes an interbody device inserted into the disc spaceseparating L5 and S1.

The present invention further contemplates instruments for use duringsurgical procedures that are used to secure an anterior supplementalfixation plate to the spine. One such instrument includes a plate holderthat includes a holding portion mounted on a shaft. The holding portionmatches the shape of the lower edge of the plate and is provided withmeans for establishing and maintaining a defined relative positionbetween the holding portion and the plate. The instrument furtherincludes a support member having guiding portions for directing screwsinto the plate holes.

The present invention further includes methods for stabilizing a spinalsegment. One method includes installing a generally triangular-shapedplate having an upper node along the anterior face of L5 and a pair oflower nodes along the anterior face of S1; installing a first screw fromthe front of the plate through a single hole in the upper node of theplate into L5; and installing screws from the front of the plate througha hole in each of the lower nodes of the plate and into S1. Variationsto the above method and other methods are also contemplated.

The above is intended merely as a summary of various inventive aspectspresented in the present application, and is in no way intended to be anexhaustive or all-inclusive recitation of such aspects. Additionalaspects, forms, features, embodiments and principles of the presentinvention will be further described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic representation of the region of vertebrae L5-S1where a plating system according to the invention is implanted.

FIG. 2 is a representation of the region and plating system of FIG. 1viewed in profile.

FIGS. 3 a-3 d show, respectively, a plan view, a cross section along 3b-3 b of FIG. 3 a, a cross section along 3 c-3 c of FIG. 3 a, and across section along 3 d-3 d of FIG. 3 a, of an example of a plateaccording to the present invention.

FIG. 4 is a perspective view of another embodiment of a plate accordingto the present invention.

FIG. 5 is a perspective view of a plate according to the presentinvention equipped with one embodiment of a retaining element.

FIG. 6 is a side view of the retaining element on the plate of FIG. 5.

FIGS. 7 a and 7 b show, respectively, a plan view and a view in crosssection along 7 b-7 b of FIG. 7 a of another embodiment retainingelement.

FIGS. 8 a and 8 b are perspective views of a plate according to theinvention equipped with a retaining element according to the example inFIG. 7, the retaining element being either in a non-retaining position(FIG. 8 a) or in a retaining position (FIG. 8 b.).

FIG. 9 is a perspective view of a tool which can be used for securing aplate of the present invention to the L5-S1 region.

FIG. 10 shows the tool from FIG. 9 equipped with a pusher which can beused during fitting of the plate.

FIG. 11 shows the tool from FIG. 9 equipped with a rod for drillingholes into the vertebrae which will accommodate the screws for fixingthe plate.

FIG. 12 shows a side view of another embodiment of the tool of FIG. 9.

FIG. 13 is a perspective view of another embodiment of a tool which canbe used for securing a plate of the present invention to the L5-S1region.

FIG. 14 a is a perspective view of a plate according to the presentinvention equipped with another embodiment retaining element

FIG. 14 b is a perspective view looking at the posterior side of theplate and retaining element of FIG. 14 a.

FIGS. 15 a and 15 b show, respectively, a plan view and a cross-sectionthrough line 15 b-15 b of FIG. 15 a of the retaining element of FIG. 13.

FIG. 16 is a perspective view of another embodiment plate according tothe present invention.

FIG. 17 is a perspective view of the posterior side of the plate of FIG.16.

FIG. 18 is a cross-section taken along line 18-18 of FIG. 17.

FIG. 19 is a perspective view of a portion of the plate of FIG. 16 witha deformation tool applied thereto.

FIG. 20 is a perspective view of another embodiment plate according tothe present invention.

FIG. 21 is a perspective view of yet another embodiment plate accordingto the present invention.

FIG. 22 is a perspective view of still a further embodiment plateaccording to the present invention.

FIG. 23 is a perspective view of the posterior side of the plate of FIG.22.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended. Any such alterations and furthermodifications in the illustrated devices, and any such furtherapplications of the principles of the invention as illustrated thereinare contemplated as would normally occur to one skilled in the art towhich the invention relates.

The present includes a plate in the shape of a triangle. In oneapplication, the plate is inserted in the space available between theleft iliac vein and the right iliac artery. The plate is adapted in thisway minimize or eliminate interference with the anatomy at the site ofimplantation. The triangular shape gives the plate a large effectivesurface area while minimizing the risk of its coming into contact withthe blood vessels during its fitting and afterwards. The plate is fixedto the vertebrae by three fixation screws near the vertices of thetriangle. In one specific application, the upper screw is fixed tovertebra L5, while the lower two screws are fixed to vertebra S1. Whilethe plate described herein is particularly useful for application alongthe anterior aspect of the spinal column in the L5-S1 region,application along the lateral aspects or antero-lateral aspects of thespinal column and also in other regions of the spine is alsocontemplated.

Referring now to FIG. 1, there is a diagrammatic representation of thelumbo- sacral region viewed anteriorly. FIG. 1 shows the last lumbarvertebrae L4, L5 and the first sacral vertebrae S1. L4, L5 and S1 areeach separated by discs D. The main blood vessels present in this regionare also shown, namely the vena cava 1, which divides at L5 into theright iliac vein 2 and the left iliac vein 3, and the aorta 4 whichdivides at L5 into the right iliac artery 5 and the left iliac artery 6.The space available in the region between the left iliac vein 3 andright iliac artery 5 makes it difficult to secure a conventional platehaving appropriate load carrying capabilities to the L5-S1 junction froman anterior approach.

The plate 7 according to the invention has a generally triangular shapein order to adapt to the space available for its implantation. Holes 8,9, 10 are provided in the plate 7 to permit its fixation by means ofscrews 11, 12, 13 penetrating into the vertebrae L5 and S1. A first hole8 is formed near the upper vertex of plate 7 in an upper node 8 a. Uppernode 8 a is intended to be placed adjacent vertebra L5 so that screw 11penetrates into L5 adjacent its lower margin or edge 14, as isillustrated in FIG. 2. The other two holes 9, 10 are formed near thelower vertices of plate 7 in lower nodes 9 a and 10 a, respectively.Lower nodes 9 a and 10 a are intended to be placed adjacent vertebra S1so that screws 12, 13 penetrate into S1 adjacent its upper margin oredge 15, as can be seen in FIG. 2. The vertices of plate 7 are roundedto minimize trauma to adjacent tissue.

The fixation of the screws 11, 12, 13 on the margins 14, 15 of thevertebrae concerned, in orientations defined by the configurations ofthe holes 8, 9, 10, overcomes the problems associated with the differentangulations between these vertebrae. These differences in angulation arerelated to the differing profiles of the vertebrae. It is furthercontemplated that the size of plate 7 can be reduced so that it does notextend substantially beyond the margins 14, 15 and the edges of theplate smooth and rounded to minimize trauma when in contact withadjacent tissue. While it is contemplated that the overall configurationof plate 7 can be standardized and provided in a range of sizes, theexternal dimensions can also vary depending on the patient anatomydetermined according to pre-operative modeling of the L5-S1 region forthe particular patient.

In one specific embodiment, screws 11, 12, and 13 are cancellous bonescrews. It is further contemplates that screws 11, 12, and 13 can be anytype of bone engaging fastener known in the art. The underside of theheads of screws 11, 12, and 13 can be rounded above the smooth shankportions of the screws received in the holes 8, 9, and 10. The roundedscrew heads allow the screws to become well seated in a curved seatingsurface formed in plate 7 around holes 8, 9, and 10, thus permittingsome angulation of the screws relative to the plate 7 as the screws areinstalled and tightened in place.

FIGS. 3 a-3 d show plate 7 in further detail. As illustrated edges 16,17, 18 of plate 7 are concave to minimize the lateral and caudal extentof plate 7 between nodes 8 a, 9 a and 10 a. Plate 7 can have a shapebetween edges 16, 17, and 18 that has a slightly concave curvature onits posterior or lower face 23 in order to better adapt to the anatomyof the spinal column and also a slightly convex curvature along anterioror upper face 19 to minimize anterior protrusion. Hole 8 forimplantation of screw 11 in L5 is configured to give screw 11 asignificant inclination at an angle a relative to the directionperpendicular to anterior face 19 of plate 7. Holes 9, 10 forimplantation of the screws 12, 13 in S1 are configured to give screws12, 13 a substantially perpendicular orientation relative to theanterior face 19 of the plate 7. As discussed above, it is alsocontemplated that screws 12, 13 can be provided with a head having aspherical lower bearing surface so that screws 12 and 13 can assume anyone of multiple angular orientations with anterior face 19. Plate 7 alsoincludes near its lower edge 17 an opening 20 and near its lower nodes 9a and 10 a indents 21 and 22, respectievly. Opening 20 and indents 21,22 are intended to allow the plate 7 to be gripped by means of a tooladapted for this purpose, it being understood that hole 20 and indents21 and 22 constitute only one particular example of such means which cancooperate with a gripping tool. Examples of such a tool will bedescribed below.

Posterior face 23 of plate 7 is intended to be directed towards thevertebrae. Posterior face 23 has a protrusion 24 extending along atleast part or substantially all of its width. Protrusion 24 has an upperface 25 that is positioned and configured to bear against the lower lipof the anterior margin 14 of the lower endplate of L5, as can be seen inFIG. 2. The oblique orientation of screw 11 tends to press protrusion 24against L5, which strengthens the hold of plate 7 on L5 and resists anypivoting effect of plate 7 about screw 11 that may result upon lateralflexion of the spine. As is shown, plate 7 also includes protrusions 26,27 on its posterior face 23 in the area of lower nodes 9 a, 10 a, alongthe edges of plate 7. Protrusions 26, 27 are placed along S1 and bearagainst the anterior face of S1 adjacent margin 15, as can be seen inFIG. 2, so as to help hold plate 7 in place. The anchoring of plate 7 onL5 can also be complemented by a ridge-shaped upper lip 28 (FIGS. 3 band 3 c), or by one or more points 734 (FIG. 23), formed adjacent edges16, 18 and extending from posterior face 23 of the plate 7 in the regionof upper node 8 a in the area of its contact with the anterior face ofL5.

Plate 7 also includes a central opening 29 intended to permit insertionand securement of a retaining element for blocking screws 11, 12, 13inserted through holes 8, 9 and 10, respectively. Plate 7 includes twoopenings 30, 31 cooperating with the retaining element. The function ofthe retaining element is to prevent screws 11, 12, 13 from tending toescape from their receiving seat after they have been tightened ontoplate 7.

FIG. 5 shows a plate 7 identical to that in FIG. 3, equipped with afirst example of a retaining element 32. Retaining element 32 has acircular or substantially circular shape, the diameter of which allowsretaining element 32 partially covers holes 8, 9, 10 after screws 11,12, 13 are inserted. Retaining element 32, also shown in FIG. 6,includes a central opening 33 and two openings 34, 35 situated on eitherside of central opening 33. Openings 34, 35 correspond in location toopenings 30, 31 of plate 7. Retaining element 32 includes a lower face36 that includes extending therefrom a series of elastic tabs 37distributed about central opening 33. It is contemplated that at leasttwo or more tabs 37 are provided. The lower end of each tab 37 includesa beveled end 38 and a bearing surface 40.

After fixation of plate 7 to the vertebrae, retaining element 32 can beput into place on plate 7 in the following way. Using a suitable toolthat includes two rods penetrating openings 34, 35 of retaining element32, retaining element 32 is brought into position toward plate 7, andthe ends of the rods are introduced into openings 30, 31 of plate 7.Retaining element plate 32 is then pushed against plate 7 so as tointroduce elastic tabs 37 into central opening 29 of plate 7. Beveledends 38 facilitate this introduction and deflect tabs 37 inwardly towardone another during this introduction. Tabs 37 are thus fitted in centralopening 29 of plate 7 and prevent retaining element 32 from becomingdislodged from plate 7. A bearing surface 39 (FIG. 3 b, 3 d) is formedin central opening 29 of plate 7 to cooperate with bearing surface 40formed on beveled end 38 of each tab 37. Retaining element 32 can thusbe installed by clipping it onto plate 7, and can be dislodged therefromusing a suitable tool that can pry tabs 37 from hole 29. It should beunderstood that other techniques for positioning retaining element 32 onplate 7 are also contemplated, including simply manually placing tabs 37in hole 29.

Another embodiment of the plate of the present invention is provided inFIG. 4. Plate 107 is generally identical to plate 7 discussed aboveexcept as otherwise noted below. Plate 107 includes holes 109, 110 thathave an oblong shape so as to give the surgeon more freedom for thelocation of implantation of screws 12, 13 in S1. Oblong holes 109, 110further allow plate 107 to adapt to the postoperative changes in themorphology of the patient. However, in the FIG. 4 embodiment hole 108that receives screw 11 implanted in L5 has a shape exactly adapted tothat of the head of screw 11 and prohibits any relative displacementbetween plate 107 and screw 11 at this level to provide good stabilityfor the implanted plate 107

Another embodiment retaining element is shown in FIGS. 7 a and 7 b.Retaining element 132 is not circular here but has on its peripherythree cutouts 142, 143, 144 that form flange like projections 142 a, 143a and 144 a. Like retaining element 32, retaining element 132 includes alower face 136, a central opening 133, and elastic tabs 137 aboutcentral opening 133 with beveled ends 138 and bearing surfaces 140. Tofacilitate rotation with a tool, three openings 145, 146, 147 are formedon retaining element 132, offset 120° relative to one another aboutcentral opening 133. A U-shaped opening 148 is also formed in order todefine an elastic tongue 149 that lifts when a force is exerted on itsposterior face 150. The end of the tongue 149 has a stud 151 on itsposterior face.

Retaining element 132 is used as follows. Referring to FIGS. 8 a and 8b, retaining element 132 can be placed on plate 107 before screwinsertion. Retaining element 132 is initially placed on plate 107 sothat cutouts 142, 143, 144 leave holes 108, 109, 110 of plate 107entirely exposed, as shown in FIG. 8 a, permitting insertion andtightening of screws 11, 12, 13 upon positioning of plate 107 on thevertebrae. The positions and dimensions of cutouts 142, 143, 144 arechosen accordingly. With retaining element 132 in this position, stud151 of tongue 150 is engaged in a receiving seat 131 (FIG. 4) formed onanterior face 119 of plate 107. Plate 107 is then put into place andscrews 11, 12, 13 are tightened. A suitable tool is then inserted in oneor more of openings 145, 146, 147 of retaining element 132, andretaining element 132 is turned 180° with the aid of this tool. Underthe effect of the force applied to it, stud 151 is released from itsseat and permits rotation of retaining element 132. Consequently,flanged portions 142 a, 143 a, 144 a of retaining element 132 partiallycover holes 108, 109, 110 as shown in FIG. 8 b. Retaining element 132thus prevents screws 11, 12, 13 from backing out beyond anterior face119. Retaining element 132 is held in this position by virtue of theengagement of stud 151 in a receiving seat 130 (FIG. 4.) The pre-fittingof retaining element 132 on plate 107 prior to positioning plate 107 onthe vertebrae of the patient eliminates the fiddle factor for thesurgeon.

Plate 107 of the osteosynthesis device in FIG. 8 has oblong holes 109,110, but it is understood that retaining element 132 can also be used onplate 7 which has circular holes 9, 10. Those skilled in the art willreadily appreciate that the clippable retaining elements 32, 132described above can have different configurations than those shownherein and still block screws seated in the plate holes.

The present invention also includes an instrument designed forpositioning the plates and screws of the present invention as shown inFIGS. 9-11. Instrument 50 will be described with respect to plate 7, itbeing understood that instrument 50 has application with the other plateembodiments described herein.

Instrument 50 includes a plate holding portion 52 which matches theshape of lower edge 17 of plate 7. Holding portion 52 includes studs(not shown) that are inserted into indents 21, 22. It is furthercontemplate that holding portion 52 and plate 7 can be provided with anyother means of establishing a defined relative position therebetween.Instrument 50 further includes a shaft 53 which is bent and has a grip54 at its proximal end to allow the surgeon to manipulate instrument 50and plate 7. Shaft 53 has adjacent its distal end a distal portion 55perpendicular to anterior surface 19 that supports holding portion 52.

It is contemplated that at least distal portion 53 is hollow, andinstrument 50 further includes a rod 56 extending through the hollowdistal portion 55 of shaft 53. Rod 56 can be provided with threads andheld on shaft 53 by a corresponding thread on an inner wall surface ofshaft 53. The distal end of rod 56 lodges in opening 20 of plate 7. Theinner wall surface of opening 20 can include a thread corresponding to athread on the lower end of rod 56. The proximal end of rod 56 opens tothe outside of shaft 53 and has a recess 57 for insertion of ascrewdriver. Tightening and loosening rod 56 makes it possible for plate7 and holding portion 52 to be connected and disconnected.

Instrument 50 also includes a tube 58 which can pass through shaft 53and is connected to it. Tube 58 has an inner passage that allows a rod59 to be inserted therein and held in position in its internal space.Rod 59 includes at its lower end a point 60 which bears on or embeds invertebra S1 upon positioning of plate 7 thereon. Instrument 50 furtherincludes a support 61 attached to shaft 53 and arranged substantiallyhorizontally. Support 61 includes a lateral arm 61 a extending to aguide member 61 b that includes three guiding portions 62, 63, 64. Firstguiding portion 62 is formed on the side of guide member 61 b adjacentshaft 53 and second and third guiding portions 63 and 64 are formed onthe side of guide member 61 opposite shaft 53.

Use of instrument 50 to secure plate 7 will now be described. In a firststep, plate 7 is fixed on holding portion 52 as described above. Thesurgeon then positions plate 7 on L5 and S1 at the desired site. Plate 7can be held at the desired site by penetrating point 60 of rod 59 intoS1. Pusher 65, as shown in FIG. 10, is also used to firmly seat plate 7on L5 and S1. Pusher 65 is a shaft which has at its proximal end a grip66 and at its distal end a bulb 67 which can lodge in hole 8 of plate 7.Bulb 67 could also lodge in a depression or a hole provided in plate 7specially adapted for this purpose. Bulb 67 can be replaced by any othermeans capable of ensuring its function of maintaining the position ofpusher 65 bearing on plate 7.

In a second step, pusher 65 is withdrawn and the holes intended toreceive screws 11, 12, 13 are drilled in L5 and S1. This drilling iscarried out, as is shown in FIG. 11, using a drill rod 68. Drill rod 68includes at a proximal end a grip 69 and at a distal end a bit 70capable of drilling a hole in a vertebra to receive a screw. To drill ahole in L5, as is shown in FIG. 11, drill rod 68 is guided through hole8 of plate 7, and applied against guiding portion 62 of support 61. Theposition of support 61 and the shape of guiding portion 62 aredetermined in such a way that the angle of penetration of the drill tipin L5 corresponds to the desired angle of penetration of screw 11. Oncethe hole in L5 is completed, the holes in S1 for receiving screws 12, 13are then drilled in a similar manner. The drill rod, however, isoriented away from grip 54 in order to provide the appropriate caudalorientation of screws 12 and 13. Drill rod 68 is then guided throughhole 9 and guiding portion 63 of support 61, and through hole 10 andguiding portion 64 of support 61 to drill holes in S1.

Finally, screws 11, 12, 13 are inserted in the holes which have justbeen drilled and are tightened by means of a conventional screwdriver,which can also be applied against support 61 in a manner similar to whatwas done for drill rod 68. Plate 7 is then disconnected from holdingportion 52 by loosening rod 56. The procedure is completed by puttinginto place a retaining element to block screws 11, 12, 13, if such aretaining element were provided.

It is contemplated that holding portion 52 can be detachable from shaft53 to allow the use different sizes of plate holding portions 52.Various holding portions 52 can be provided that are based on variousexternal dimensions of different sized plates 7. Likewise, for theoptimum choice of the points of penetration and the values of the anglesof penetration of screws 11, 12, 13, the position and orientation ofsupport 61 and its guiding portions can be determined and adjusted bythe surgeon before and during the procedure.

Another embodiment of instrument 50 is shown in FIG. 12 and designatedas 50′. The elements of instrument 50′ common to instrument 50 aredesignated therein by the same reference numbers. In this embodiment,tube 58 and rod 59 are replaced by a flexible rod 71 arranged alongshaft 53 and passing through its proximal end via a hole 72. At thedistal end of flexible rod 71 there is a rigid rod 73 which ends in abearing surface 74 that will rest on S1 upon positioning of plate 7 at asuitable angle therewith. Flexing of rod 71 provides an indication tothe surgeon when such contact between bearing surface 74 and S1 is made.

It will be understood that variants in the details of the design ofinstrument 50 described herein are contemplated. For example, the meansfor connecting and disconnecting plate 7 and holding portion 52 can bedifferent than those described. It is possible to use, for example, aninstrument in which the distal end of rectilinear portion 55 of shaft 53can be clipped/unclipped to cooperate with hole 20 of plate 7. Forexample, as shown in FIG. 13, instrument 50″, except as otherwise noted,is the same as instrument 50 and like elements are designated with thesame reference numerals. Instrument 50″ includes a plate holding portion52″ that includes a foot 72 having a hole 73 therethrough. A fastener 75extends through hole 73 and engages foot 72 to hole 29 of plate 7. Foot72 can include a stud (not shown) extending downwardly therefrom that ispositionable in hole 20 to prevent rotation of plate 7 about fastener75. With instrument 50″ plate 7 need not include indents 21, 22,although provision of the same is not precluded.

Referring now to FIGS. 14 a-14 b, another embodiment plate 207 is shown.Plate 207 is identical to plates 7, 107 except with respect to itsretaining element 232, and that plate 207 does not include indents forcoupling to a plate holder, although the provision of such indents isnot precluded. Plate 207 includes upper hole 208 extending through uppernode 208 a, first lower hole 209 extending through first lower node 209a, and second lower hole 210 extending through second lower node 210 a.Plate 207 includes edges 216, 217, 218 extending between anterior face212 and posterior face 214. A retaining element 232, shown in furtherdetail in FIGS. 15 a-15 b, is secured to anterior face 212 of plate 207and partially overlaps holes 208, 209, 210 when screws 11, 12 and 13 arepositioned therein.

Retaining element 232 is secured to plate 207 by a locking fastener 230that threadingly engages a central hole 229 of plate 207. Retainingelement 232 has a generally triangular shape with rounded apices thatgenerally match the outer edge profile of plate 207. Retaining element232 can include a hole 235 that can be used to assist in placing lockingelement 232 to its proper positioning on anterior face 212 or to holdretaining element 232 in position as locking fastener 230 is threadedinto hole 229. Locking fastener 230 engages a central hole 238 ofretaining element 232 and contacts lip 239 extending therearound to holdit against anterior face 212. As shown in FIG. 14 b, locking fastener230 also extends through hole 229 to posterior face 214. Hole 229 hasinwardly biased tangs 236 extending therearound at its lower opening,which can be recessed with respect to posterior face 214. Tangs 236clamp onto locking fastener 230 and prevent it from unthreading.

It is contemplated that retaining element 232 can be provisionallyfastened to plate 207 with locking fastener 230 threaded partially intohole 229 before placement of plate 207 on the vertebrae. In this manner,retaining element 232 is rotatable with respect to anterior face 212,and can oriented such that holes 208, 209, and 210 are not blockedthereby. After screws 11, 12 and 13 are inserted to secure plate 207 tothe vertebrae, retaining element 232 can be oriented to its FIG. 14 aposition and locking fastener 230 advanced in hole 229 to engage tangs236.

Referring now to FIGS. 16-19, another embodiment plate 407 is shown.Plate 407 is identical to plates 7, 107 except with respect to theconfiguration of the retaining elements and their attachment to plate407, and also in that plate 407 does not include indents for coupling toa plate holder, although the provision of such indents is not precluded.Plate 407 includes edges 416, 417, 418 extending between an anteriorface 412 and a posterior face 414. Plate 407 can further include upperprotrusion 432 along posterior face 414 for contacting the lower marginof L5. Plate 407 further includes a central hole 436 and a lowerinstrument engaging hole 438 that can be used to engage an insertioninstrument.

Plate 407 includes an upper node 420 a, a first lower node 420 b and asecond lower node 420 c each having a screw hole 422 a, 422 b, 422 c,respectively, formed therethrough. Upper retaining element 424 a isconnected with anterior face 412 of plate 407 by a connecting element426 a that is formed as an integral unit with plate 407 and upperretaining element 424 a. A gap 430 a is formed between upper retainingelement 424 a and anterior face 412. Upper retaining element 424 aextends at least partially around upper hole 422 a and, in its FIG. 16position, allows entry of a screw 11 through upper hole 422 a forattachment to L5. After screw 11 is seated in upper hole 422 a, upperretaining element 424 a can be bent or deformed from its first form ofFIG. 16 to a second form shown in FIG. 19. In its second form upperretaining element 424 a extends over upper hole 422 a and blocks screw11 if it were to unseat from upper hole 422 a and backout from plate407.

There is further provided first and second lower retaining elements 424b, 424 c associated with first lower node 420 b and second lower node420 c, respectively. First and second lower retaining elements 424 b,424 c are connected with anterior face 412 of plate 407 by connectingelements 426 b, 426 c, respectively, that are formed as an integral unitwith plate 407 and first and second lower retaining elements 424 b, 424c. Gaps 430 b, 430 c are formed between each first and second lowerretaining element 424 b, 424 c, respectively, and anterior face 412.Each of the first and second lower retaining elements 424 b, 424 cextends at least partially around a corresponding one of the first andsecond lower holes 422 b, 422 c. In their FIG. 16 position, first andsecond lower retaining elements 424 b, 424 c allow entry of screws 12,13 through first and second lower holes 422 b, 422 c for attachment toS1. After screws 12, 13 are seated in first and second lower holes 422b, 422 c, first and second lower retaining elements 424 b, 424 c aredeformed or bent by, for example, applying a bending force, from theirfirst form of FIG. 16 to a second form shown in FIG. 19. In their secondform, first and second lower retaining elements 424 b, 424 c each extendover respective ones of first and second lower holes 422 b, 422 c andblock a corresponding one of the screws 12, 13 if one were to unseatfrom its hole and backout from plate 407.

Plate 407 also provides an alternate arrangement for posteriorprotrusion 432 intended to contact L5. As shown in FIG. 18, protrusion432 is intercepted by hole 422 a and is thus not continuous along thewidth of plate 407. In contrast, protrusion 24 of plate 7 is situatedbelow hole 8 and is continuous along the width of plate 7. It should beunderstood, however, that the location of the L5 posterior protrusionfor the plates described herein can be varied based on patient anatomyand either of the above locations for the L5 posterior protrusion can beprovided with any of the plate embodiments described herein.

As also shown in FIG. 19, there is providing a forming tool 450 that isoperable to simultaneously apply a bending force to retaining elements424 a, 424 b, 424 c to move these retaining elements from their firstform to their second form overlapping the adjacent plate hole. Tool 450has an outer shaft 452 coupled to a distal working end 454. Distalworking end 454 includes a first forming member 456 a positionableadjacent upper retaining element 424 a, a second forming member 456 bpositionable adjacent first lower retaining element 424 b, and a thirdforming member (not shown) positionable adjacent second lower retainingelement 424 c when tool 450 is mounted on central hole 436 of plate 407.The forming members 456 a, 456 b are wedge shaped and are pivotallycoupled to working end 454 at upper ends 458 a, 458 b and their oppositethicker lower ends 460 a, 460 b are normally biased towards the centerof shaft 452. An inner actuator 462 housed in outer shaft 452 andworking end 454 is movable with respect thereto in the direction ofarrow P. Actuator 463 slides distally along the wedge-shaped formingmembers and pivots their lower ends about their respective upper endsand away from the center of tool 450 into contact with the adjacentretaining element.

Tool 450 is representative of one type of instrument that can be used tobend or adjust the formable retaining elements from their first form totheir second form. Other instruments and techniques are alsocontemplated. For example, the retaining elements can be individuallybent or adjusted by a tool inserted into the gap along the retainingelement and manipulated therein to apply a bending force. The retainingelements can also be made from a shape memory alloy and temperatureapplied thereto in order to form the retaining element from their firstform to their second form Referring now to FIG. 20, another embodimentplate 507 is shown. Plate 507 is identical to plate 407 except withrespect to the configuration of the retaining elements and theirattachment to plate 507. Plate 507 includes an upper node 520 a, a firstlower node 520 b and a second lower node 520 c each having a screw holeformed therethrough. A base member 526 is connected to or formed as anintegral unit with plate 507 and extends from its anterior face 512.Base member 526 has an upper retaining element 524 a adjacent upper hole522 a, a first lower retaining element 524 b adjacent first lower hole522 b, and a second lower retaining element 524 c adjacent second lowerhole 522 c. Gaps 530 a, 530 b, and 530 c are formed between base member526 and respective ones of the retaining elements 524 a, 524 b and 524c. Retaining elements 524 a, 524 b and 524 c are illustrated in FIG. 20in their first form allowing screw insertion into the adjacent holes. Asdiscussed above with respect to retaining elements of plate 407,retaining elements 524 a, 524 b and 524 c can be bent or otherwise movedinto a second form after screw insertion wherein the retaining elementsextend over the holes of plate 507 and prevent screw backout.

Referring now to FIG. 21, another embodiment plate 607 is shown. Plate607 is identical to plate 407 except with respect to the configurationof the retaining elements and their attachment to plate 607. Plate 607includes an upper node 620 a, a first lower node 620 b and a secondlower node 620 c each having a screw hole formed therethrough. Plate 607includes a wall 626 around its perimeter and around holes 622 a, 622 b,622 c. Wall 626 forms a central opening 627 in the middle of plate 607,and wall 626 separates central opening 627 and holes 622 a, 622 b, and622 c. Central opening 627 enables visualization of an implant I in thedisc space and accommodates insertion of a forming tool, such as tool450 discussed above, alongside upper retaining element 624 a adjacentupper hole 622 a, first lower retaining element 624 b adjacent firstlower hole 622 b, and second lower retaining element 624 c adjacentsecond lower hole 622 c. Gaps 630 a, 630 b, and 630 c are formed betweeneach retaining element 624 a, 624 b, 624 c and wall 626, respectively.Retaining elements 624 a, 624 b and 624 c are illustrated in FIG. 21 intheir first form allowing screw insertion into the adjacent holes. Asdiscussed above with respect to retaining elements of plate 407,retaining elements 624 a, 624 b and 624 c can be bent or moved to asecond form after screw insertion wherein the retaining elements extendover the holes of plate 607 and prevent screw backout. Further, cutouts633 a, 633 b, and 633 c are provided in the recess of the hole adjacentretaining elements 624 a, 624 b, and 624 c, respectively, to receive aforming tool inserted therein, which tool can then be pivoted to bendthe adjacent retaining element.

Referring now to FIGS. 22-23, another embodiment plate 707 is shownthat-is generally the same as the other plate embodiments discussedherein except as otherwise noted below. Plate 707 includes an upper node720 a and first and second lower nodes 720 b, 720 c. Upper node 720 aand lower nodes 720 b, 720 c each have a hole for receiving a bone screw11, 12, 13, respectively. Plate 707 further includes an anterior face712 and an opposite posterior face 714. The edges of plate 707 are notconcave between the nodes, but could be provided as such. In thisembodiment, plate 707 is provided with a pair of spikes 734 extendingfrom posterior face 714 at the upper end of plate 707. Spikes 714 areembeddable in the upper vertebral body to which the plate is to besecured, such as L5. Such spikes could likewise be provided with any ofthe plate embodiments described herein.

Plate 707 further includes a retaining element 726 rotatably attached tocentral hole 736 in the middle of plate 707 by a pin 730. Retainingelement 726 has an upper apex 724 a, first lower apex 724 b and secondlower apex 724 c. Retaining element 726 has a first position (not shown)wherein retaining element 726 is positioned with respect to plate 707 sothat apices 724 a, 724 b, 724 c are not positioned over the screw holesthrough the plate nodes 720 a, 720 b, 720 c. After screw insertion,retaining element 726 is rotated with respect to plate 707 to positionapices 724 a, 724 b, 724 c over the screw holes through nodes 720 a, 720b, 720 c to prevent screw backout. A spring blade 728 is initiallypositioned substantially within a slot 732 formed in retaining element726. Spring blade 728 can be moved out of slot 732 and into contact withanterior face 712 to prevent further rotation of retaining element 726.The orientation between spring blade 728 and anterior face 712 can besuch that anterior face 712 biases spring blade 728 upward to providefrictional engagement therebetween causing spring blade 728 to remain inits extended position shown in FIG. 22.

Further embodiments of retaining elements for blocking screws 11, 12, 13are also contemplated. For example, the anterior face of the plate couldbe provided with a seat open on one side and bordered by rails orgrooves that allow the retaining element to be slidably inserted thereinafter the screws have inserted. The retaining element could be held inthe receiving seat by means of an elastic tongue having formed on itslower face a stud which, upon complete insertion of the retainingelement, will penetrate into a receiving seat formed on the anteriorsurface of the plate

Various means are described herein for securing the retaining element onthe plate, such as clips, locking fasteners, and pins. Clippableretaining elements, either pre-fitted or not pre-fitted, areadvantageous since the retaining element can secured to the plate easilyand quickly. The only manipulations by the surgeon required by clippableretaining elements that are not pre-fitted is to move the retainingelement in a direction perpendicular to the plate in the space whichcorresponds to that which was necessary to form anyway for positioningthe plate on the spinal column. Use of sliding elements is alsocontemplated, which necessitate the formation of an additional space toaccommodate sliding insertion of the retaining element if not pre-loadedon the plate. The present invention also contemplates retaining elementssecured by a threaded fastener and can either be preloaded on the plateor not preloaded on the plate. It should be understood that the presentinvention contemplates the use of any of the retaining elementembodiments described herein with any of the plate embodiments describedherein.

Examples of material which may be employed in fabrication of the platesand retaining elements of the present invention can be made from anybio-compatible non-resorbable material, such as titanium, stainlesssteel, shape memory alloys, and combinations thereof. Resorbablematerials are also contemplated. In the embodiments of FIGS. 16-21, thebody of the plate can be made from titanium, and the retaining elementsmade from a shape memory alloy that is formable from the first formallowing screw insertion to the second form for blocking the insertedscrews. In another example, the retaining elements can be made from amaterial less resistant to bending forces than the plate body, whichwould allow the retaining elements to be more easily bent by thesurgeon.

The plate assembly of the present invention may also be used incombination with various types of implants I (FIG. 2). Examples of suchimplants include interbody spacers, fusion device, and bone graftmaterials that are placed in disc space D. Further examples of suchdevices include bone dowels, push-in cages, screw-in cages, taperedcages, cages filled with bone graft and/or graft substitute material orother types of devices suitable for such fusion applications.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges and modifications that come within the spirit of the inventionare desired to be protected.

1. A plating apparatus for the spine, comprising: a plate having agenerally triangular shape and having an upper node and a pair of lowernodes; an upper hole in the plate at the upper node to receive a screwfor passage into an L5 vertebra; and a first lower hole in the plateformed through one of the lower nodes to receive a screw for passageinto the S1 vertebra and a second lower hole in the plate through theother of the lower nodes to receive a screw for passage into the S1vertebra.
 2. The apparatus of claim 1, wherein said plate has lateraledges extending between said upper node and each of said lower nodes,said lateral edges having a concave profile.
 3. The apparatus of claim1, wherein said plate includes at least one spike extending from aposterior face of said plate positionable into the L5 vertebra.
 4. Theapparatus of claim 1, wherein said plate has a posterior facepositionable against the L5 vertebra and the S1 vertebra, said posteriorface having a concave profile.
 5. The apparatus of claim 4, wherein saidplate includes a protrusion extending from said posterior face adaptedto contact the inferior margin of the L5 vertebra.
 6. The apparatus ofclaim 5, wherein said lower nodes each have a thickened portion adaptedto conform to the profile of anterior face of the S1 vertebra.
 7. Theapparatus of claim 1, wherein said upper hole has a screw axis orientedat an angle with respect to an axis extending perpendicular to ananterior face of said plate.
 8. The apparatus of claim 1, wherein saidplate has a central hole located between said upper node and said pairof lower nodes.
 9. The apparatus of claim 8, wherein said plate includesa retaining element attachable to said central hole.
 10. The apparatusof claim 9, wherein said retaining element has a generally triangularshape.
 11. The apparatus of claim 9, wherein said retaining element hasa circular shape.
 12. The apparatus of claim 9, wherein said retainingelement has three cutouts positionable adjacent respective ones of saidholes to allow screw passage into said holes, said cutouts definingflanges therebetween, wherein said retaining element is movable withrespect to said plate so that said flanges block screws inserted intosaid holes.
 13. The apparatus of claim 1, wherein said plate includes aretaining element adjacent each of said upper hole and said first andsecond lower holes, each of said retaining elements having a first formwherein a screw is insertable into the adjacent hole and being formableto a second form wherein said retaining element extends over theadjacent hole. 14-21. (Cancelled)
 22. A plating apparatus for the spine,comprising: a plate having a generally triangular shape with an uppernode positionable along an upper vertebra and a pair of lower nodespositionable along a lower vertebra; an upper hole in the plate at theupper node to receive a screw for engaging the upper vertebra; a firstlower hole in the plate through one of the lower nodes to receive ascrew for engaging the lower vertebra and a second lower hole in theplate through the other of the lower nodes to receive a screw forengaging the lower vertebra; and means for blocking screws inserted inthe upper hole and the first and second lower holes.
 23. The apparatusof claim 22, wherein said means for blocking includes a triangularretaining element attached to said plate, said retaining element beingmovable from a first orientation wherein screws are insertable into eachof said upper hole and said first and second lower holes to a secondorientation wherein apices of said retaining element extend overrespective ones of said upper hole and said first and second lowerholes.
 24. The apparatus of claim 23, wherein said retaining elementincludes a spring blade extendable therefrom to secure said retainingelement in said second orientation.
 25. The apparatus of claim 23,wherein said retaining element includes a locking fastener extendingtherethrough and engageable to a central hole in said plate to securesaid retaining element in said second orientation.
 26. The apparatus ofclaim 22, wherein said means for blocking includes a retaining elementadjacent respective ones of said upper hole and said first and secondlower holes.
 27. The apparatus of claim 26, wherein each of saidretaining elements has a first form wherein a screw is insertable insaid adjacent hole and is deformable to a second form wherein saidretaining element extends over said adjacent hole.
 28. A method ofstabilizing the L5 and S1 vertebrae, comprising: installing a generallytriangular-shaped plate having an upper node along the anterior face ofthe L5 vertebra and a pair of lower nodes along the anterior face of theS1 vertebra; installing a first screw through a single hole in the uppernode of the plate into L5; and installing second and third screwsthrough a hole in each of the lower nodes of the plate and into S1. 29.The method of claim 28 and further comprising installing a retainingelement on the plate to block the first, second and third screws intheir respective holes.
 30. The method of claim 28 and furthercomprising rotating a retaining element pre-fitted on the plate to blockthe first, second and third screws in their respective holes.
 31. Themethod of claim 28 and further comprising inserting a fusion device inthe disc space between the L5 and S1 vertebrae before installing theplate.
 32. The method of claim 31 and further comprising coupling theplate to an instrument having a guiding portion for guiding a drill andscrew placement into each of said holes before installing the plate. 33.A plating apparatus for the spine, comprising: a plate having a generaltriangular shape, said plate having an upper hole near an upper vertexthrough which a screw is passed for securing said plate to the L5vertebra, and a pair of lower holes situated near respective ones offirst and second lower vertices of said plate, each of said pair oflower holes having a screw passed therethrough to secure said plate tothe S1 vertebra.
 34. The apparatus of claim 33, wherein said plateincludes a posterior face having a protrusion extending along at leastpart of the width of said plate that bears against a lower lip of ananterior margin of a lower endplate of the L5 vertebra.
 35. Theapparatus of claim 34, wherein said plate includes on said posteriorface adjacent said pair of lower vertices protrusions that bear againsta lower margin of an upper endplate of the S1 vertebra.
 36. Theapparatus of claim 33, wherein said plate includes a posterior facehaving an edge about said plate, said posterior face including a ridgeshaped protrusion adjacent said edge at the upper end of said uppervertex.
 37. The apparatus of claim 33, wherein said plate includes aposterior face having an edge about said plate, said posterior faceincluding an anchoring point extending therefrom adjacent said uppervertex.
 38. The apparatus of claim 33, wherein said plate includes aposterior face having a generally concave shape.
 39. The apparatus ofclaim 33, wherein said pair of lower holes have an oblong shapeextending in the direction toward said upper vertex.
 40. The apparatusof claim 33, further comprising means for blocking screws seated in saidupper hole and said pair of lower holes.
 41. The apparatus of claim 40,wherein said means for blocking screws includes a retaining elementattachable to a central hole in said plate, said retaining elementconfigured to at least partially cover said upper hole and said pair oflower holes.
 42. The apparatus of claim 41, wherein said retainingelement has a substantially circular shape.
 43. The apparatus of claim41, wherein said retaining element includes means for fixing saidretaining element on said plate either in a first angular positionleaving said upper hole and said pair of lower holes completelyuncovered, or in a second angular position at least partially coveringsaid upper hole and said pair of lower holes.
 44. The apparatus of claim43, wherein said means for fixing said retaining element includes anelastic tongue including a stud extending from a posterior face of saidretaining element, said stud insertable in receiving seats formed on ananterior face of said plate.
 45. The apparatus of claim 40, wherein saidmeans for blocking screws includes a retaining element threadinglyattached to a central hole in said plate, said retaining element beingconfigured to at least partially cover said upper hole and said pair oflower holes.
 46. The apparatus of claim 40, wherein said means forblocking screws includes a retaining element which can be screwed ontosaid plate.
 47. The apparatus of claim 46, wherein said retainingelement has a generally triangular shape.
 48. The apparatus of claim 40,wherein said means for blocking screws includes a retaining elementhaving three projecting flanges and cutouts between said flanges,whereby each of said flanges is positionable between respective adjacentones of said upper hole and said pair of lower holes for screwinsertion, said retaining element being movable to a second positionwherein each of said flanges at least partially covers respective onesof said upper hole and said pair of lower holes.
 49. A system for fusionof the L5 and S1 junction of the spine, comprising: a plate having atriangular shape, said plate having an upper vertex positionable over L5and lower vertices positionable over S1, each of said vertices having ahole formed therethrough; three screws, each of said screws positionedthrough a corresponding one of said holes to secure said plate to L5 andS1; and an interbody fusion device positioned in the disc space betweenL5 and S1.
 50. The system of claim 49, wherein said interbody fusiondevice includes a bone graft. 51-57. (Cancelled)